Sorted Strings Table (SSTable) is the persistent file format used by Scylla and Apache Cassandra. SSTable is saved as a persistent, ordered, immutable set of files on disk.
Immutable means SSTables are never modified; they are created by a MemTable flush and are deleted by a compaction.
The location of Scylla SSTables is specified in scylla.yaml data_file_directories parameter (default location: /var/lib/scylla/data).

All Scylla versions (Enterprise and Open Source) up to Scylla Open Source 3.0 used Apache Cassandra 2.x SSTable compatible format (known as ‘la’). Scylla Open Source 3.0 now supports the Apache Cassandra 3.x format (‘mc’) which is more efficient and requires less disk space than the Scylla 2.x.